In production of organic compounds, some malodorous materials may be generated by reaction or remain after reaction, which can not only result in working environment pollution and working efficiency reduction but also place a burden on the environment and human health.
Deodorization techniques used conventionally include, for example, cleaning methods, adsorption methods, combustion methods, biological deodorization methods, ozone deodorization methods, photo-catalyst deodorization methods, plasma deodorization methods, refresher or deodorizer methods, and dilution or diffusion methods. Generally, in each of these deodorization methods, the generated malodorous material is once directed to outside the reaction system and then treated outside the reaction system using an appropriate deodorization technique.
In addition, cleaning, adsorption, and combustion methods are generally used in combination because malodorous materials generated by chemical reaction contain an organic solvent used in the reaction.
However, the combination of such methods described above has problems such as manufacturing equipment enlargement, high costs, and high environmental burden. In addition, the process of directing malodorous materials to outside the reaction system requires a measure to prevent the diffusion of the malodor from the manufacturing equipment, such as a closed system for the entire equipment, which increases the equipment cost.
There has been proposed a method of removing malodorous materials from foods and beverages using a hollow fiber membrane (see Patent Literature 1), in which the malodorous materials are not those generated by chemical reaction or remaining after chemical reaction. Unfortunately, this method is not practical for removing malodorous materials generated by chemical reaction or remaining after chemical reaction, owing to problems with the solvent resistance of the membrane to organic solvents for use in reactions or in view of the cost required to introduce treatment equipment.
Oxidation reactions for synthesizing aldehyde or ketone compounds by oxidation of alcohol compounds are typical examples of chemical reactions in which the reaction step can generate an offensive odor material being a malodorous material or the odor material can remain after the reaction step. Such oxidation reactions are very important for organic synthesis. Swern oxidation is a typical oxidation reaction. Swern oxidation is widely used as laboratory-scale oxidation because it does not generate any heavy metal-containing waste, has a wide range of applicable compounds, and does not bring about excessive oxidation. However, Swern oxidation has the problem of by-production of dimethyl sulfide, which is toxic and strongly malodorous, after the oxidation reaction, because it uses oxalyl chloride or trifluoroacetic anhydride, and dimethyl sulfoxide (DMSO) as activators (see Non-Patent Literature 1).
Corey-Kim oxidation is a useful method that uses reaction conditions milder than those for Swern oxidation and can selectively produce an aldehyde or ketone compound from an alcohol compound even when the alcohol compound has an oxidation-sensitive substituent, such as an amino group, in the molecule (Non-Patent Literature 2). However, measures against the offensive odor of dimethyl sulfide (DMS) are a problem with Corey-Kim oxidation, which uses dimethyl sulfide and N-chlorosuccinimide as activators. There has been also developed a modified method using dodecyl methyl sulfide, which is less malodorous (see Patent Literature 2). However, such a method has problems such as high cost and complicated treatment of the sulfide compound after the reaction.
Therefore, Swern oxidation and Corey-Kim oxidation have not been popular for industrial use, though they are very useful for the synthesis of aldehyde or ketone compounds by oxidation reaction of alcohol compounds.